An animal model system employing the Chlamydia psittaci agent of guinea pig inclusion conjuctivitis (GPIC) and guinea pigs will be used to further investigate immunity, pathogenesis, and potential consequences of chlamydial genital tract infections. The effect of immunosuppression using cyclophosphamide will be studied in male guinea pigs infected intraurethrally wth GPIC. Animals will be monitored for duration of shedding of the agent, humoral and cell-mediated immune responses, and histopathologic effects determined by immunofluorescence, light and electron microscopy. Anti-guinea pig thymocyte serum will be investigated for immunosuppressive effect and influence on GPIC genital infection in female guinea pigs. Response to serum therapy by intravaginal administration of anti-GPIC serum will be further investigated in the prevention of salpingitis in infected Cy-treated animals. The feasibility of immunization aganist genital tract infection by administration of killed vaccine directly in the genital tract will be explored. Major emphasis will be directed to further development of a new convenient animal model system employing mice and the Chlamydia trachomatis agent of mouse pneumonitis.